A host of pests feed on cucumber leaves, including the cucumber beetle, the flea beetle, slugs, snails and the variegated cutworm. Deer and rabbits may also eat cucumber leaves, though the prickliness of the leaves may deter them if there is something more tender to eat in the garden.
Though the larvae of the cucumber beetle eat the roots of the plant, the midsummer brood of adults eat and lay their eggs on the leaves of cucumber plants. The cucumber beetle, however, often lays its eggs on only one plant or leaf, so destroying this plant or leaf will get rid of many cucumber beetles.
The beetle itself is small, with a black head and a solid yellow or yellow-green back. Some types of cucumber beetle have three black stripes on the back, while another variety is spotted. Of all the types of cucumber beetles, the striped variety is most destructive to cucumbers.
The flea beetle is a tiny black or brown beetle that jumps if threatened. Signs of these beetles are small holes in the leaves that appear early in the summer. Flea beetle infestations are worst in areas that have experienced a mild winter and a cool, wet spring.